//生产环境使用的webpack，把公共js、css提取出来并且压缩源代码

const autoprefixer = require('autoprefixer');
const path = require('path');
//访问内置的插件
const webpack = require('webpack');
//自动生成一个html文件插件
const HtmlWebpackPlugin = require('html-webpack-plugin');
// 导入非 webpack 默认自带插件
//将样式抽取出来为独立的文件
const ExtractTextPlugin = require('extract-text-webpack-plugin');
//生成一个指定名称的json文件
const ManifestPlugin = require('webpack-manifest-plugin');
//允许我们将自定义变量插入
const InterpolateHtmlPlugin = require('react-dev-utils/InterpolateHtmlPlugin');
//用于缓存外部项目依赖关系。
const SWPrecacheWebpackPlugin = require('sw-precache-webpack-plugin');
//静态代码检查
const eslintFormatter = require('react-dev-utils/eslintFormatter');
//确保从应用程序的源目录中进行的相对导入不会在其外部导入
const ModuleScopePlugin = require('react-dev-utils/ModuleScopePlugin');
const paths = require('./paths');
const getClientEnvironment = require('./env');

// Webpack uses `publicPath` to determine where the app is being served from.
// It requires a trailing slash, or the file assets will get an incorrect path.
const publicPath = paths.servedPath;
// Some apps do not use client-side routing with pushState.
// For these, "homepage" can be set to "." to enable relative asset paths.
const shouldUseRelativeAssetPaths = publicPath === './';
// `publicUrl` is just like `publicPath`, but we will provide it to our app
// as %PUBLIC_URL% in `index.html` and `process.env.PUBLIC_URL` in JavaScript.
// Omit trailing slash as %PUBLIC_URL%/xyz looks better than %PUBLIC_URL%xyz.
const publicUrl = publicPath.slice(0, -1);
// Get environment variables to inject into our app.
const env = getClientEnvironment(publicUrl);

// Assert this just to be safe.
// Development builds of React are slow and not intended for production.
if (env.stringified['process.env'].NODE_ENV !== '"production"') {
    throw new Error('Production builds must have NODE_ENV=production.');
}

// Note: defined here because it will be used more than once.
const cssFilename = 'static/css/[name].[contenthash:8].css';


const extractTextPluginOptions = shouldUseRelativeAssetPaths ? {publicPath: Array(cssFilename.split('/').length).join('../')} : {};

module.exports = {
    // Don't attempt to continue if there are any errors.
    bail: true,
    // We generate sourcemaps in production. This is slow but gives good results.
    // You can exclude the *.map files from the build during deployment.
    devtool: 'source-map',
    // In production, we only want to load the polyfills and the app code.
    entry: [require.resolve('./polyfills'), paths.appIndexJs],
    
    output: {

        path: paths.appBuild,

        filename: 'static/styles/[name].[chunkhash:8].js',
        //chunks 选项的作用主要是针对多入口(entry)文件
        chunkFilename: 'static/styles/[name].[chunkhash:8].chunk.js',
        // We inferred the "public path" (such as / or /my-project) from homepage.
        publicPath: publicPath,

        devtoolModuleFilenameTemplate: info =>
            path.relative(paths.appSrc, info.absoluteResourcePath),
    },
    
    resolve: {
        // This allows you to set a fallback for where Webpack should look for modules.
        // We placed these paths second because we want `node_modules` to "win"
        // if there are any conflicts. This matches Node resolution mechanism.
        // https://github.com/facebookincubator/create-react-app/issues/253
        modules: ['node_modules', paths.appNodeModules].concat(
            // It is guaranteed to exist because we tweak it in `env.styles`
            process.env.NODE_PATH.split(path.delimiter).filter(Boolean)
        ),
        // These are the reasonable defaults supported by the Node ecosystem.
        // We also include JSX as a common component filename extension to support
        // some tools, although we do not recommend using it, see:
        // https://github.com/facebookincubator/create-react-app/issues/290
        extensions: ['.js', '.json', '.jsx'],
        alias: {
            // Support React Native Web
            // https://www.smashingmagazine.com/2016/08/a-glimpse-into-the-future-with-react-native-for-web/
            'react-native': 'react-native-web',
            components: path.resolve(__dirname, '..') + '/src/components',
            container: path.resolve(__dirname, '..') + '/src/container',
            images: path.resolve(__dirname, '..') + '/src/assets/images',
            pages: path.resolve(__dirname, '..') + '/src/pages',
            utils: path.resolve(__dirname, '..') + '/src/utils',
            data: path.resolve(__dirname, '..') + '/src/server/data',
            actions: path.resolve(__dirname, '..') + '/src/redux/actions',
            reducers: path.resolve(__dirname, '..') + '/src/redux/reducers',
        },
        plugins: [
            // Prevents users from importing files from outside of src/ (or node_modules/).
            // This often causes confusion because we only process files within src/ with babel.
            // To fix this, we prevent you from importing files out of src/ -- if you'd like to,
            // please link the files into your node_modules/ and let module-resolution kick in.
            // Make sure your source files are compiled, as they will not be processed in any way.
            new ModuleScopePlugin(paths.appSrc),
        ],
    },
    
    module: {
        strictExportPresence: true,
        rules: [
            // TODO: Disable require.ensure as it's not a standard language feature.
            // We are waiting for https://github.com/facebookincubator/create-react-app/issues/2176.
            // { parser: { requireEnsure: false } },

            // First, run the linter.
            // It's important to do this before Babel processes the JS.
            {
                test: /\.(js|jsx)$/,
                enforce: 'pre',
                use: [
                    {
                        options: {
                            formatter: eslintFormatter,

                        },
                        loader: require.resolve('eslint-loader'),
                    },
                ],
                include: paths.appSrc,
            },
            // ** ADDING/UPDATING LOADERS **
            // The "file" loader handles all assets unless explicitly excluded.
            // The `exclude` list *must* be updated with every change to loader extensions.
            // When adding a new loader, you must add its `test`
            // as a new entry in the `exclude` list in the "file" loader.

            // "file" loader makes sure those assets end up in the `build` folder.
            // When you `import` an asset, you get its filename.
            {
                exclude: [/\.html$/, /\.(js|jsx)$/, /\.css$/, /\.less$/, /\.json$/, /\.bmp$/, /\.gif$/, /\.jpe?g$/, /\.png$/,],
                loader: require.resolve('file-loader'),
                options: {
                    name: 'static/media/[name].[hash:8].[ext]',
                },
            },
            // "url" loader works just like "file" loader but it also embeds
            // assets smaller than specified size as data URLs to avoid requests.
            {
                test: [/\.bmp$/, /\.gif$/, /\.jpe?g$/, /\.png$/],
                loader: require.resolve('url-loader'),
                options: {
                    limit: 10000,
                    name: 'static/media/[name].[hash:8].[ext]',
                },
            },
            // Process JS with Babel.
            {
                test: /\.(js|jsx)$/,
                include: paths.appSrc,
                loader: require.resolve('babel-loader'),
                options: {

                    // This is a feature of `babel-loader` for webpack (not Babel itself).
                    // It enables caching results in ./node_modules/.cache/babel-loader/
                    // directory for faster rebuilds.
                    plugins: [
                        "transform-decorators-legacy",
                        ['import', [{libraryName: 'antd', style: true}]],  // import less
                    ],
                    cacheDirectory: true,
                },
            },
            // The notation here is somewhat confusing.
            // "postcss" loader applies autoprefixer to our CSS.
            // "css" loader resolves paths in CSS and adds assets as dependencies.
            // "style" loader normally turns CSS into JS modules injecting <style>,
            // but unlike in development configuration, we do something different.
            // `ExtractTextPlugin` first applies the "postcss" and "css" loaders
            // (second argument), then grabs the result CSS and puts it into a
            // separate file in our build process. This way we actually ship
            // a single CSS file in production instead of JS code injecting <style>
            // tags. If you use code splitting, however, any async bundles will still
            // use the "style" loader inside the async code so CSS from them won't be
            // in the main CSS file.
            {
                test: /\.css$/,
                loader: ExtractTextPlugin.extract(
                    Object.assign(
                        {
                            fallback: require.resolve('style-loader'),
                            use: [
                                {
                                    loader: require.resolve('css-loader'),
                                    options: {
                                        importLoaders: 1,
                                        minimize: true,
                                        sourceMap: true,
                                    },
                                },
                                {
                                    loader: require.resolve('postcss-loader'),
                                    options: {
                                        ident: 'postcss', // https://webpack.js.org/guides/migrating/#complex-options
                                        plugins: () => [
                                            require('postcss-flexbugs-fixes'),
                                            autoprefixer({
                                                browsers: [
                                                    '>1%',
                                                    'last 4 versions',
                                                    'Firefox ESR',
                                                    'not ie < 9', // React doesn't support IE8 anyway
                                                ],
                                                flexbox: 'no-2009',
                                            }),
                                        ],
                                    },
                                },
                            ],
                        },
                        extractTextPluginOptions
                    )
                ),
                // Note: this won't work without `new ExtractTextPlugin()` in `plugins`.
            },
            // Parse less files and modify variables
            {
                test: /\.less$/,
                use: [
                    require.resolve('style-loader'),
                    require.resolve('css-loader'),
                    {
                        loader: require.resolve('postcss-loader'),
                        options: {
                            ident: 'postcss', // https://webpack.js.org/guides/migrating/#complex-options
                            plugins: () => [
                                require('postcss-flexbugs-fixes'),
                                autoprefixer({
                                    browsers: [
                                        '>1%',
                                        'last 4 versions',
                                        'Firefox ESR',
                                        'not ie < 9', // React doesn't support IE8 anyway
                                    ],
                                    flexbox: 'no-2009',
                                }),
                            ],
                        },
                    },
                    {
                        loader: require.resolve('less-loader'),
                        options: {
                            modifyVars: {"@primary-color": "#1DA57A"},
                        },
                    },
                ],
            },
            // ** STOP ** Are you adding a new loader?
            // Remember to add the new extension(s) to the "file" loader exclusion list.
        ],
    },
    
    plugins: [
        // Makes some environment variables available in index.html.
        // The public URL is available as %PUBLIC_URL% in index.html, e.g.:
        // <link rel="shortcut icon" href="%PUBLIC_URL%/favicon.ico">
        // In production, it will be an empty string unless you specify "homepage"
        // in `package.json`, in which case it will be the pathname of that URL.
        new InterpolateHtmlPlugin(env.raw),
        // Generates an `index.html` file with the <script> injected.
        new HtmlWebpackPlugin({
            inject: true,
            template: paths.appHtml,
            minify: {
                removeComments: true,
                collapseWhitespace: true,
                removeRedundantAttributes: true,
                useShortDoctype: true,
                removeEmptyAttributes: true,
                removeStyleLinkTypeAttributes: true,
                keepClosingSlash: true,
                minifyJS: true,
                minifyCSS: true,
                minifyURLs: true,
            },
        }),
        // Makes some environment variables available to the JS code, for example:
        // if (process.env.NODE_ENV === 'production') { ... }. See `./env.styles`.
        // It is absolutely essential that NODE_ENV was set to production here.
        // Otherwise React will be compiled in the very slow development mode.
        new webpack.DefinePlugin(env.stringified),
        // Minify the code.
        new webpack.optimize.UglifyJsPlugin({
            compress: {
                warnings: false,
                // Disabled because of an issue with Uglify breaking seemingly valid code:
                // https://github.com/facebookincubator/create-react-app/issues/2376
                // Pending further investigation:
                // https://github.com/mishoo/UglifyJS2/issues/2011
                comparisons: false,
            },
            output: {
                comments: false,
            },
            sourceMap: true,
        }),
        // Note: this won't work without ExtractTextPlugin.extract(..) in `loaders`.
        new ExtractTextPlugin({
            filename: cssFilename,
        }),
        // Generate a manifest file which contains a mapping of all asset filenames
        // to their corresponding output file so that tools can pick it up without
        // having to parse `index.html`.
        new ManifestPlugin({
            // 生成的文件名字，选填
            fileName: 'asset-manifest.json',
        }),
        // Generate a service worker script that will precache, and keep up to date,
        // the HTML & assets that are part of the Webpack build.
        new SWPrecacheWebpackPlugin({
            // By default, a cache-busting query parameter is appended to requests
            // used to populate the caches, to ensure the responses are fresh.
            // If a URL is already hashed by Webpack, then there is no concern
            // about it being stale, and the cache-busting can be skipped.
            dontCacheBustUrlsMatching: /\.\w{8}\./,
            filename: 'service-worker.js',
            logger(message) {
                if (message.indexOf('Total precache size is') === 0) {
                    // This message occurs for every build and is a bit too noisy.
                    return;
                }
                console.log(message);
            },
            minify: true,
            // For unknown URLs, fallback to the index page
            navigateFallback: publicUrl + '/index.html',
            // Ignores URLs starting from /__ (useful for Firebase):
            // https://github.com/facebookincubator/create-react-app/issues/2237#issuecomment-302693219
            navigateFallbackWhitelist: [/^(?!\/__).*/],
            // Don't precache sourcemaps (they're large) and build asset manifest:
            staticFileGlobsIgnorePatterns: [/\.map$/, /asset-manifest\.json$/],
            // Work around Windows path issue in SWPrecacheWebpackPlugin:
            // https://github.com/facebookincubator/create-react-app/issues/2235
            stripPrefix: paths.appBuild.replace(/\\/g, '/') + '/',
        }),
        // Moment.styles is an extremely popular library that bundles large locale files
        // by default due to how Webpack interprets its code. This is a practical
        // solution that requires the user to opt into importing specific locales.
        // https://github.com/jmblog/how-to-optimize-momentjs-with-webpack
        // You can remove this if you don't use Moment.styles:
        new webpack.IgnorePlugin(/^\.\/locale$/, /moment$/),
    ],
    // Some libraries import Node modules but don't use them in the browser.
    // Tell Webpack to provide empty mocks for them so importing them works.
    node: {
        fs: 'empty',
        net: 'empty',
        tls: 'empty',
    },
};
